The present invention relates to the treatment of isocyanate residues. It is well known to prepare isocyanates by reacting the corresponding amine with phosgene in an organic solvent following phosgenation, the resulting isocyanate is generally vacuum distilled to improve the purity of the resultant product. This distillation procedure produces an undistillable residue. The chemical composition of the residue is not clear, and the residue itself poses a disposal problem. The prior art is replete with attempts to utilize and/or treat the above-mentioned isocyanate residue. Typical of such treatments are reaction with aromatic phenols (U.S. Pat. No. 3,084,182), hydrolysis (U.S. Pat. Nos. 3,128,310, 3,331,876, 4,091,009, 4,137,266, and 4,311,800), ammonolysis (U.S. Pat. No. 3,210,395), reaction with various active-hydrogen containing materials (U.S. Pat. Nos. 3,180,852, 3,755,215, and 4,032,574), and grinding the residue and thereafter suspending the resultant ground material (U.S. Pat. Nos. 4,251,401 and 4,297,456). To date, none of these techniques have alleviated the problem of the waste management of the isocyanate residues.
The present invention is directed to the discovery of a relatively simple technique for treating isocyanate distillation residues. The treatment results in a yellow solid powder and an aqueous liquid phase that for distillation residues of many isocyanates is nearly colorless or lightly colored. The liquid phase can be easily treated as waste water, whereas the solid powder can be readily used as a filler material for polyurethane-based resins and foams.